This invention relates to oceanographic instrumentation and more particularly, to a system for cyclically measuring ocean characteristics between two levels.
Data gathering of oceanographic parameters has increased in recent years. Primarily, the prior art has utilized moored current meters to gather data representative of currents, as well as moored meters for temperature and other ocean characteristics. Time series recording of these data has been generated from fixed instruments on taut-wire moorings in the deep ocean and on continental shelf and slope locations. However, it has been observed that with the conventional current and other characteristic monitoring systems, long-term measurement in the near-surface region of the open ocean has been particularly difficult, particularly when data gathering has been taken within 200 meters of the surface. The data has exhibited gross dynamic errors introduced by the surface wave field. This upper ocean region is particularly important in studies since the dynamics are based on energy transfer between the atmosphere and the deep ocean. In addition, a significant amount of the horizontal transport of heat momentum takes place in that region.
The energy in horizontal currents is contained mainly is low frequency motions, with geostropic, tidal, and inertial motions accounting for the great bulk of the energy. In view of this relative low frequency of the parameter changes, unattended vertical profilers with periodic sampling have been developed in the prior art for monitoring certain scaler and vector quantlties in the upper ocean. As an example of the prior art, U.S. Pat. No. 3,952,349 to Erath, et al. discloses a variable buoyancy device for automatically cycling an object, or platform having instrumentation, between upper and lower limits. This variable buoyancy device utilizes control of mean density to provide the cyclic vertical motion. The density control is accomplished by means of an inflatable bladder which is used together with a compressed gas supply and valve assembly to change the displacement of the system. In operation, the bladder is alternately inflated to control the buoyancy to be negative at a preselected low external pressure, and discharged into the ocean to control the buoyancy to be positive at a preselected high external pressure. Consequently, the instrumentation package coupled to the buoyant device cycles between the specified pressure points in the ocean. However, for long-term missions, this form of buoyancy control requires a relatively large bulk and mass apparatus particularly for gas storage.
It is an object of the present invention to provide an improved system for measuring ocean parameters.
It is another object of the present invention to provide an improved system for measuring ocean parameters, including a compact means for sustaining cyclic vertical motion throughout long-term immersion.